Selective syntheses and fragmentation reactions of cationic cyclo-Phosphanes

除碳元素外，磷最容易形成homo原子环和簇状化合物。这一事实已经反映在磷的各种元素修饰中，其中P4分子是最具活性的修饰。形成较强P-P单键（200 kJ/mol）的趋势也反映了聚膦化合物的多样性和通用性。在这方面，以通式PnRn （R = alkyl, aryl）为特征的单环多膦化合物的化学也在文献中得到了很好的记载，因此，几十年来，磷化学已经成为一个迷人而丰富的领域。然而，对于以n -杂环碳烯（NHC）或环烷基（氨基）碳烯（cAAC）为取代基的阳离子型LnPnn+和LnRmPn+mn+的合成及其反应性尚不甚了解。通过我们的阳离子四磷酸烷的合成，我们希望建立一个完整的阳离子环磷烷库，其中环的大小主要由磷原子上的取代基控制。此外，取代基L和R的取代模式（电子和空间性质）将控制阳离子环膦的合成。下一步，开发新的策略，形成阳离子环磷化，我们将集中在深入的反应性研究。在本项目结束时，我们希望通过高效合理的路线对所提出的合成阳离子环磷烷的方法有一个深刻而基本的了解。对于对称和混合取代环膦的反应性研究，我们将重点关注与主族元素化合物的反应。不同的反应模型，如断裂反应，插入和转移反应，环扩张反应和氧化还原反应将被开发。由于该项目具有基础性和探索性，因此我们将进入环磷化领域的新领域，因此，我们提出的许多反应不是先验的可预测的。我们相信我们提出的许多反应途径将独立地导致有趣和令人兴奋的磷化合物。对称和混合取代环膦反应行为的一般结构将得到发展，这将是本项目的主要成果。在这方面，深入的机理研究的实施具有重大的影响，以确定反应中间体和副产物。

Next to the element carbon, phosphorus has the highest affinity to build-up homo atomic ring and cluster compounds. This fact mirrors already in the diverse element modifications of phosphorus, from which the P4 molecule is the most reactive modification. The tendency to form comparatively strong P–P single bonds (200 kJ/mol) also reflects the diverse and versatile class of compounds of polyphosphanes. In this regard, the chemistry of monocyclic polyphosphanes featuring the general formula PnRn (R = alkyl, aryl) is also well documented in literature and thus, a fascinating and abundant field of phosphorus chemistry already for decades. However, there is not very much known about the synthesis and the reactivity of cationic cyclo-phosphanes featuring the general formula LnPnn+ and LnRmPn+mn+ where the onio-substituent L derives from N-heterocyclic carbenes (NHC) or cyclic alkyl(amino)carbenes (cAAC). With our synthesis of the cationic tetraphosphetane, we hope to establish a novel route to a whole library of cationic cyclo-phosphanes, for which the ring size is mostly controlled by the substituents at the phosphorus atom. Also the substitution pattern (electronic and steric properties) of the substituents L and R will control the ring size for the synthesis of the cationic cyclo-phosphanes. Next to the development of novel strategies to form cationic cyclo-phosphanes, we will focus on in-depth reactivity studies. At the end of this project, we hope to gain a profound and fundamental understanding of the presented methods to synthesize cationic cyclo-phosphanes via efficient and rational routes. Regarding the reactivity studies on the symmetric and mixed-substituted cyclo-phosphanes, we will focus on reactions with main group element compounds. Different reaction models such as fragmentation reactions, insertion- and transfer reactions, ring expansion reactions and redox reactions will be developed. As this project is of fundamental and explorative nature, we will herewith enter new areas in the field of cyclo-phosphanes and thus, many of our proposed reactions are not a priori predictable. We believe that many of our suggested reaction pathways will independently lead to interesting and exciting phosphorus compounds. A general constitution of the reaction behavior of symmetric and mix-substituted cyclo-phosphanes will be developed and will be a major result of this project. In this regard, the implementation of in-depth mechanistic studies owns a significant impact in order to identify reactive intermediates and side-products.